Saturday, July 9, 2011

PHYSICS PRINCIPLES BEHIND THE BULLET TRAINS OF JAPAN(PART-1)

PHYSICS PRINCIPLES BEHIND THE BULLET TRAINS OF JAPAN
The design features of Japan’s Shinkansen 500-Series exemplifies biomimicry in action. Its overhead pantograph sports serrations were modeled on the design of owl plumage to reduce air resistance noise, and the air piercing
nose cone design was inspired by the kingfisher’s beak

The ‘SHINKANSEN’ bullet trains of Japan has been named as one among the ‘Historic Mechanical Engineering Landmarks’, and the name is true to its potential since we will see the principles that have gone into its operation and the ingenious solutions found by the Japanese engineers to the problems faced by high-speed rails.  

(1) TRACKS AND WHEEL ALIGNMENT
Who makes Japan's railway wheels and axles?
Sumitomo Metals is the only manufacturer of railway wheels and axles in Japan. Sumitomo Metals also makes 100% of the most important components that support the safety of railway vehicles, including those on Shinkansen bullet train lines, conventional railway lines, and subway lines. Japan's high-speed railway technology is currently leading the world.

Effect of high-speed rail on tracks and the body of train : ‘HUNTING OSCILLATIONS’
top view                                                                                                                                             front view
“Hunting oscillation is a swaying motion of a railway vehicle caused by the coning action on which the directional stability of an adhesion railway depends. It arises from the interaction of adhesion forces and inertial forces”
At low speed, adhesion dominates but, as the speed increases, the adhesion forces and inertial forces become comparable in magnitude and the oscillation begins at a critical speed. Above this speed, the motion can be violent, damaging track and wheels and potentially causing derailment.
 Example of Hunting oscillation:
tracks curled due to the effect in West Germany

ANCIENT PRINCIPLE EMPLOYED TO OVERCOME OSCILLATIONS :
EARLY MECHANICAL CLOCK
A mainspring is a spiral torsion spring of metal ribbon that is the power source in mechanical watches and some clocks. Winding the timepiece, by turning a knob or key, stores energy in the mainspring by twisting the spiral tighter. The force of the mainspring then turns the clock's wheels as it unwinds, until the next winding is needed.
‘main spring’ seen inside an early mechanical clock

All 'mechanical’ oscillating clocks, mechanical work similarly and can be divided into analogous parts. They consist of an object that repeats the same motion over and over again, an oscillator, with a precisely constant time interval between each repetition, or 'beat'. Attached to the oscillator is a controller device, which sustains the oscillator's motion by replacing the energy it loses to friction, and converts its oscillations into a series of pulses. The pulses are then added up in a chain of some type of counters to express the time in convenient units, usually seconds, minutes, hours, etc.

Implementation in trains:
   springs seen in the side attachments to the wheels in bogies
 
  The springs prevent the side-ward motion as the spring action is vertical.

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